In 1775-1783, Jean-Emmanuel Gilibert (1741-1814) stayed in Respublica Poloniae to oranize a veterinary school, the Royal Botanic Garden and the Royal School of Physicians in Grodno, and since 1781 he worked in Vilnius as Professor of Natural History at the Principal School of the Grand Duchy of Lithuania. Little is known about his work conducted in Lithuania in the field of geology and earth sciences. The author has decided, on the basis of Gilibert's publications and analysis of the literature (works of J. Garbowska and P. Daszkiewicz and others), to present his teaching and research activities in this field. In Grodno, Gilibert looked after and multiplied the collections of the natural history cabinet at the Royal School of Physicians, renowned for its rich mineralogical and fossil collections watched and admired by, among others, King Stanisław August, J. Bernoulli (1744-1807) and M. Patrin (1742-1815) who mentions the amber rosary with a different species of insects preserved in each bead. Gilibert's tours around Lithuania were the opportunity to enlarge the geological collections and to adapt them to the needs of the school. He also appreciated the importance of ordinary specimens representing the geology of the area. These specimens not only enriched the natural history cabinet, but also defined the way of working and collecting. Ha was the first to found and gather fossil animals from near Grodno. The signs of mineralogical and geological interests of Gilibert can be found in the works of other authors of that epoch (L. Viteta (1736-1809) and J. Bernoulli). In Vilnius, Gilibert conducted a one year-long full lecture on natural history (zoology, botany and mineralogy). In his lectures on mineralogy, he presented not only the systematics, but also emphasized the usefulness of minerals in medicine, for the production of ornamental items and in different sectors of the economy. He adapted the process of teaching to the needs of practical life, based on observations and experiments, and was using the local wildlife specimens in his lectures. Thanks to the French naturalist, the teaching of natural science remained at a good European level since the time the Department was founded at the University of Vilnius. A treatise on physical geography of the Grand Duchy of Lithuania is Gilibert's best-known published work in Poland. Based on own observations, he determined, e.g., the causes of drying of ponds and marshes, as well as of the formation of peat, limonitic iron and ocher, the origin of rivers in Lithuania and the presence of amber, and described a number of fossils. He provided the characteristics of geological deposits (now included in the Quaternary), described their origin and age, and drew attention to the issues of dynamic geology (e.g. erosional activity of rainwater, river erosion, formation of sand dunes). From the period of his eight-year stay in Lithuania, Gilibert also submitted observations on the climate of Lithuania, documented by temperature measurements. He indicated that the climate of this part of Europe was milder than the French believed, with clearly noticeable two seasons: winter and summer. He pointed out that the autumn rains give rise to muddy areas persisting to the end of November, and the most severe frost, usually several days long, occurs in late December and January, when the winds blow from the northeast. June and July are typically the hottest months, but the northern winds sometimes cause July ground frosts. He compared Lithuania's climate to that of the Alpine foreland. Gilibert was the first scholar who studied the natural environment of Lithuania based on scientific principles. Interesting are his observations on the amber resin, for example, unequivocal statement that amber is a resin, at the time when the idea was still much discussed. Worth noting are the geological elements in the physiographic description of Lithuania, published by Gilibert (1806) in Histoires des Plantes d'Europe. It should also be pointed to the methodological aspect of Gilibert's works: the facts precede interpretations, the results are attempted to be universalized by transposition into areas other than those investigated by Gilibert, and the observations are linked with scientific theories, which were new at those times, in the field of geology, chemistry and physics. Gilibert's descriptions were often the first ones available to the naturalists in western and southern Europe. They were all the more valuable that contained a lot of data on the geology, meteorology, physical geography etc., useful in various fields.